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PG ecosystem actually has multiple shared nothing cluster implementations, example is www.citusdata.com, unlike RAC, where masters need to sync to accept writes
by riku_iki 1y ago
PG ecosystem actually has multiple shared nothing cluster implementations, example is www.citusdata.com, unlike RAC, where masters need to sync to accept writes, so technically write load is not distributted across servers.
- mike_hearn 1y agoCitus is great but it's just sharding. Only some very specific use cases fit within those limits, and there are cost issues too (being ha requires replicas of each node etc). RAC masters don't need to sync writes to each other, that's not how it works. Every node can be writing independently, they only communicate when one node has exclusive ownership over a block another node needs to write to, and the transfer then occurs peer to peer over rdma. But if writes are scattered they work independently.
- riku_iki 1y ago> they only communicate when one node has exclusive ownership over a block another node needs to write to and it needs to communicate that he has exclusive ownership, and also after each writes you need to invalidate cached data on other nodes, and read new data from some transactionally consistent store, which will do all heavylifting (syncing/reconciling writes), which is kinda FDB.